How short below max plunk OAL is ok? My Shadow 2 OR has a deep throat!

[MikeinGA]

I’m new to CZ’s and reloading 9mm, so I’ve been absorbing everything I can from the forums.  I ordered sample packs from Blue Bullets and made up 100 125g RN over 3.8g of Sport Pistol to an OAL of ~1.110 (based on what I’ve ready others were doing).  Last night I finally had time to plunk test my 2023 Shadow 2 Optics Ready.  Much to my surprise, it plunked out to 1.155!  That’s longer than a forum member’s chamber after he had it reamed.  Anyone else plunk tested an Optics Ready Shadow 2?  I’m wondering if CZ finally increased the chamber depth in the 2023 models, or maybe the OR Shadows?
Based on my plunk test, I made up 25 rounds of 147g RN BB’s with 3.1g of Sport pistol at OAL of 1.146, and 25 more at 1.140.  They all functioned fine, but shot about an inch or more left at 20 ft compared to the 125g BB’s or the American Eagle 115’s I’ve been shooting.  
Here’s my main question.  Would the longer OAL I loaded the 147g Bullets to vs the 125g move the point of impact to the left, or would the bullet weight difference cause this?  I’d like to keep my point of impact the same across different rounds.  Should I (or is there a reason not to) shorten up the OAL of the 147g to the 1.110 (.045 below max plunk) to match the 125g and see of that would move the POI, or is this more than likely a bullet weight issue moving POI?  
Thank you for sharing your input!

[Farmer]

No reason at all not to try it as long as you’re on the lower psi side. I have some 135 RN that I have to seat .020” deeper than a similar FN bullet from the same manufacturer. If I don’t they pattern more than a group. Sometimes it’s a matter of psi and timing and seating depth affects both. 

[shred]

Plunk test varies by bullet, so don't assume one OAL will fit all of them BTW.

 

IME changing the OAL is unlikely to move the bullet impact around much.  Especially with different bullet weights its nearly impossible to keep the same POI because the gun moves while the bullet is still in the barrel and how much it moves depends on how heavy a load and how long it's in the barrel.

[JonasAberg]

I own a Shadow 2 made in 2018 (or was it 2017?) and have always loaded to 1.153 (Alsa Pro bullets) without problems.

 

I have previously noticed a similar result you did, with my Sig X-Five Allround; heavier bullets shot just a tad left (at 25m) with a light load. 124gr was spot on.

 

 

[Runswithwood1]

I also have a shadow 2 that will plunk all the way out to 1.65, I had always heard that cz's had notoriously short Chambers even my sp01 plunks out to the 1.65, dunno why but I'll take it

[Wanna_Go_Fast]

10 minutes ago, Runswithwood1 said:

I also have a shadow 2 that will plunk all the way out to 1.65, I had always heard that cz's had notoriously short Chambers even my sp01 plunks out to the 1.65, dunno why but I'll take it

This will typically depend on bullet profile.  I ran PD FMJs for the last few years and loaded out to 1.125 without issue.  Switched to blue bullets this winter and had to set my bullet back to 1.118 to pass plunk on the same gun.

 

 

[36873687]

blues changed there profile on 125 an 147 rn little friendlier to longer ovl

[shred]

Gonna toss this in here too... how to test without loading a bunch of rounds-- 

 

 

[Blackstone45]

1 hour ago, Runswithwood1 said:

I also have a shadow 2 that will plunk all the way out to 1.65, I had always heard that cz's had notoriously short Chambers even my sp01 plunks out to the 1.65, dunno why but I'll take it

That's a very long cartridge 

[Farmer]

2 hours ago, Blackstone45 said:

That's a very long cartridge 

I was wondering if there’s any bullet in the case? 

[MikeinGA]

12 hours ago, shred said:

Gonna toss this in here too... how to test without loading a bunch of rounds-- 

I tried this, and couldn’t find any of the 147g BB to fit in any of my used cases.  I’ll try with other bullets going forward though.  Thanks for the reference!

 

 

 

[MikeinGA]

23 hours ago, shred said:

Plunk test varies by bullet, so don't assume one OAL will fit all of them BTW.

 

IME changing the OAL is unlikely to move the bullet impact around much.  Especially with different bullet weights its nearly impossible to keep the same POI because the gun moves while the bullet is still in the barrel and how much it moves depends on how heavy a load and how long it's in the barrel.

Thanks, good to know!  I’ll make up some shorter 147g just to test the theory, and use up the 147g BB’s.  I wanted to use the heavier bullets so I could use less powder, but if the 125g continue to print close to the factory 115g, I might have to stay with the 125g and spend more time hunting down powder

[MikeinGA]

I’d like to thank everyone for their responses!  When I get back next week, I’m looking forward to making up some new loads and putting this advice to good use.  I’ll report back my findings once I get a chance to try them out.